The present invention relates to a turntable device for receiving a recording disc of a disc driving apparatus that spins the recording disc thereby recording and/or playing back information. The present invention relates more particularly to the turntable device mounted to disc driving apparatuses of compact disc (CD) players, digital video disc (DVD) players, optical disc drive players, and magneto-optical (MO) disc players.
A turntable device is employed as a disc rotator in a disc driving apparatus for recording media such as CD and MO disc. The turntable spins at a rotational speed ranging from hundreds rpm to thousands rpm. The Japanese Patent Application Non-examined Publication No. H09-190675 discloses a turntable device of which disc base is formed by photo-curable resin.
The disc base made of photo-curable resin has a mirror-finished-surface with a low friction coefficient. The disc placed on the base thus is apt to slip on the base. On the contrary, the disc adheres to the mirror-surface of the base, and a user has a difficulty when removing the disc from the disc base. In addition, a removal of the disc from the base sometimes produces noises.
The turntable device mounted on such disc driving apparatuses requires the more flatness on its base because the disc is spun at a high speed and high-density-data are read and write from/to the disc. An acceptable level of surface wobble, in general, is not more than 30 xcexcm for DVD player, 20 xcexcm for DVD-ROM apparatus, and 10 xcexcm for DVD-RAM apparatus. However, because the market tendency required the disc be rotated at the higher speeds and be equipped with the higher density, the acceptable level of the surface-wobble should be more strictly controlled. Wobble of base during the operation naturally causes the disc loaded on the base to wobble. The disc wobble changes a distance between the disc and a head disposed closely to the disc so that the head could not read/write data to/from the disc correctly.
Several factors contribute to this surface wobble: accuracy of mounting a turntable to a rotary shaft of a motor that drives the turntable, accuracy of machining each component of the motor, and accuracy of assembling these components into the motor are the main factors. The surface wobble due to the motor rotation thus varies according to each turntable device and is not the same. In order to minimize this surface wobble, the machining accuracy of the motor components and the assembling accuracy thereof have been improved; however, this method of improving the accuracy has deadlocked for realizing the further flatness of the base.
Another prior art of the turntable device is disclosed by the Japanese Patent Application non-examined Publication No. H11-25555. In this prior art, a turntable made of resin is secured to a metallic rotor housing of a motor. The turntable is coated with paint comprising polyester resin in suitable quantity, and the coated material is hardened. Then the surface of the coated material is cut and processed.
When the turntable made of resin is coated with paint comprising polyester resin, mold release agent used for forming the turntable still remains on the turntable. The agent thus repels the resin sprayed for coating the turntable so that the resin cannot coat uniformly the turntable.
Other conventional turntables employ polycarbonate that is vulnerable to solvent. The turntable is therefore susceptible to being damaged when the resin including solvent is applied thereto. Turntables made of resin having a low heat-resistance, e.g. polycarbonate, hardly accept an application of resin that requires heating. When a disc base formed by resin coating is machined on the turntable made of resin, suitable adhesive strength between the turntable and base, both made of resin, cannot be expected. In other words, the turntable made of resin is oxidized while it is molded as well as it is left so that the surface of the turntable cannot keep a stable condition. The adhesive characteristics between the turntable and base thus remain unstable. As a result, the adhesive strength therebetween is weak, and the base might be come off from the turntable when the disc base is cut and processed.
The present invention addresses the problems discussed above, and aims to provide a turntable device of which disc base has a hardness more than a given level, and the base has a roughened surface. This construction allows a disc on the base to be free from slip thanks to appropriate friction between the base and disc during the driving, and also to be removed from the base with ease.
A manufacturing method of this turntable comprises the steps of:
(a) applying resin liquid mixed with fine particles;
(b) forming a disc base by hardening the liquid resin; and
(c) roughening a surface of the disc base.
This manufacturing process can realize a turntable device that can prevent a disc from slipping and adhesion to the disc base. Also the turntable manufactured by this method can control surface wobble within an acceptable level.
The disc base can be cut and processed while the turntable device is mounted to the disc driving apparatus so that appropriate friction is produced between a disc and the base as well as surface wobble can be accurately controlled.
Since resin is applied to a metallic turntable, adhesive strength therebetween is stronger than the case where both are made of resin. The structure of the present invention thus is good for being cut and processed.